The meanĭroplet Generation droplet size depends primarily on the disk rotational speed and diameter, the liquid density and surface tension, and to a lesser extent the liquid flow rate and viscosity, as well as the geometry parameters of vanes. Therefore, rotary atomization is probably the most generally successful method for producing moderately monodisperse sprays over a wide range of droplet sizes. Although this arrangement can eliminate the satellite droplets to a certain extent, it might be difficult to design such a secondary flow that would operate properly under variable practical conditions, particularly in agricultural aviation applications.[Īn attractive feature of rotary atomization is the nearly uniform droplets produced with small disks at high rotational speeds and low liquid flow rates. The velocity of the air flow is set to such a level that the satellite droplets can be dragged into the flow for collection and/or recirculation while the larger primary droplets can fly across it. This is usually done by using a separate air flow near the disk periphery. However, the satellite droplets can be separated dynamically from the larger primary droplets. Another operation problem that seems to occur most often in spinning disk atomization is the production of satellite droplets. Thus, no slippage occurs after the liquid flows into the vanes, and the liquid ejection velocity may approach the disk peripheral speed. In commercial atomizers, straight or curved radial vanes are used to prevent transverse flows of the liquid over the surface and to guide the liquid to the periphery. Therefore, conventional rotary disk atomization can generate a narrow spectrum of droplet sizes only when operating in the ligament mode at low liquid flow rates. This becomes a main drawback of flat disk atomizers, particularly at high rotational speeds. It may lead to an ejection velocity of the liquid from the disk edge much lower than the disk peripheral speed. The slippage between the liquid and the disk is a problem associated with flat disk atomizers. Atomization quality for liquids of lower viscosity is usually higher than for those with higher viscosity. In addition to these two process parameters, the generation of a uniform sheet thickness and thereby a uniform droplet size requires a large centrifugal force, a vibrationless rotation, a constant liquid flow rate, and a smooth disk/cup surface. Science and Engineering of Droplets controlled by varying the liquid flow rate and/or the rotational speed.

In the spray drying industry, advances have been made in handling high flow rates up to 2400 kg/min at high wheel peripheral speeds, yielding droplets finer than 20 µm. Atomization capabilities up to 84 kg/min can be achieved. Lower speeds on the order of 50 rps have been used when a coaxial air jet is used to assist liquid breakup. Higher speeds on the order of 2500 rps have been used when a pressurized liquid is fed onto a spinning disk. Small disks rotate at high speeds up to 1000 rps whereas large disks rotate at low speeds up to 200 rps. The diameter of the rotating surface ranges from 25 mm to 450 mm. A conical-shaped cup is more usable for high flow rates than other shapes. A symmetrical feed of liquid can be readily achieved using a cup. Atomization is carried out usually in a cylindrical or conical chamber to accommodate the umbrella like, 360° spray pattern created by rotating disk and downward air/ gas streams. An air/gas flow around the periphery of rotating surface is sometimes used to shape the spray and to assist in transporting droplets away from the atomizer. Spinning disk and rotary cup atomizers are the widely used types. The rotating surface may be a flat disk, vaned disk, cup, or slotted wheel, etc. At low liquid flow rates, droplets may form directly near the edge of the surface, whereas at high liquid flow rates, ligaments or sheets may be generated at the edge and eventually disintegrate into droplets. The equipment is suitable for producing metal and alloy powders with various melting points, such as solder, aluminum powder, magnesium powder, Sn-Pb powder, Sn-Zn powder, copper powder, stainless-steel powder and other spherical powdered materials.In a rotary atomization process, a liquid is introduced onto a rotating surface at its center and then spreads out nearly uniformly under the action of centrifugal force.

Rotary atomization is a centrifugal atomization method.

Liquid metal rotary wheel